The present invention relates to powders of tetrafluoroethylene (TFE) copolymer useful for powder coating, and a process for preparing the same.
Study and development for powders of TFE copolymer used for powder coating have proceeded on the basis of the theory that such powders preferably have spherical particle shape in a viewpoint of flowability (Japanese Tokkyo Kokai No. 240713/1985).
To roto-molding or roto-lining which has been recently utilized as a method of powder coatings, however, the above theory could not be fully applied. For instance, there are some problems such that a coating formed on a mold surface partially falls off to yield coating defects on a surface of the molded article, that a coating surface largely undulates and has continuous ball-like projections, and that a coating contains bubbles or cells because its gas content cannot be sufficiently removed.
As a result of the inventors' intensive study, it has been found out that the above-mentioned problems can be solved by using powders of TFE copolymer having particular powder properties.